Electroformed nickel-chromium alloy

ABSTRACT

An article comprising a turbine component formed of a nickel-chromium (Ni—Cr) alloy including from 2 to 50 wt % chromium balanced by nickel is disclosed. The Ni—Cr alloy is thicker than at least 125 μm to make a self-supporting turbine component, and the turbine component includes a rotor blade, a stator, or a vane. The Ni—Cr alloy is electroformed on a mandrel by providing an external supply of current to an anode and a cathode in a plating bath containing a solvent, a surfactant, and an ionic liquid including choline chloride, nickel chloride, and chromium chloride.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/914,548 filed on Dec. 11, 2013 and titled ElectroformedNickel-Chromium Alloy, the disclosure of which is hereby incorporated byreference in its entirety.

FIELD OF USE

The present disclosure relates to an electroformed nickel-chromium(Ni—Cr) alloy suitable for making a turbine component intended tooperate in hostile environments. The present disclosure also relates toprocesses for the production of a thick electroformed Ni—Cr alloycomponent.

BACKGROUND

High and low pressure turbine components including rotor blades, vanes,and stators are generally made of nickel based alloys to stand hostileenvironments including high temperature. Electroformed Ni has been usedin non-high temperature applications. Nickel has excellent hightemperature creep resistance, but poor oxidation resistance. Thus, theaddition of chromia or alumina formers to increase the oxidationresistance of the nickel based alloys is desirable, particularly forhigh temperature environment such gas turbine engines.

Electroforming is a metal forming process that builds up metalcomponents through electrodeposition. The part or component is producedby depositing a metal skin onto a base form, known as a mandrel which isremoved after the electrodeposition is done. Electroforming differs fromelectroplating in that the deposit (e.g., Ni—Cr alloy) is much thickerand can exist as a self-supporting structure when the mandrel isremoved.

Electroformed Ni—Cr alloys can provide a cost-effective technique tofabricate high temperature-resistant structures with complex geometries,tighter tolerance, and oxidation resistance. Typically,electrodeposition in the conventional plating chemistry has not beensuccessful in forming Ni—Cr alloys with high chromium content (>8% wt.,20% wt. preferred) that is substantially thicker than 10 μm.

Accordingly, it is desirable is to electroform Ni—Cr alloys thicker thanat least 10 μm to make high temperature and oxidation-resistant turbineengine parts having complex geometries and requiring tighter tolerance.Further desirable considerations include the cost effectiveness andenvironmental impact of the deposition process.

SUMMARY

According to an aspect of the present disclosure, an electroformednickel-chromium (Ni—Cr) alloy suitable for making turbine enginecomponents is disclosed. The electroformed Ni—Cr alloy comprises from 2to 50 wt % chromium balanced by nickel, wherein the electroformed Ni—Cralloy is thicker than 10 μm. The addition of chromium increases theoxidation resistance of the nickel based alloys.

According to an aspect of the present disclosure, an article comprisinga Ni—Cr alloy including from 2 to 50 wt % chromium balanced by nickel isdisclosed. The article includes a turbine component, and the Ni—Cr alloyis thicker than 125 μm to make a self-supporting turbine component.

According to another aspect of the present disclosure, a method forelectroforming a thick nickel-chromium (Ni—Cr) alloy that is suitablefor making turbine components is disclosed. The method includesproviding a plating bath containing a solvent, a surfactant, and anionic liquid including choline chloride, nickel chloride, and chromiumchloride, wherein a molar ratio of the choline chloride and chromiumchloride ranges from 0.5 to 3.5, and the solvent comprises from 5 to 80vol. % relative to a mixture of the choline chloride and metal chloridesincluding the nickel and chromium chlorides. The method further includeselectroforming the Ni—Cr alloy on a mandrel, i.e. cathode by providingan external supply of current to an anode and the cathode, wherein themandrel is removed after the Ni—Cr alloy is electroformed. Optionally,the method further comprises applying a protective coating on the Ni—Cralloy to impart oxidation resistance to the turbine component.

The method further includes electroforming a Ni—Cr alloy on a metallicmandrel cathode while using an anode that is either insoluble or solublesuch as nickel under electrolytic conditions. Specifically, theinsoluble anode is used to promote the oxidation of water to produceoxygen as the main by-product while other minor products can be producedconcurrently as well. The soluble nickel anode is used to replenish thenickel deposited onto the cathode.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, that the followingdescription and drawings are intended to be exemplary in nature andnon-limiting.

The details of one or more embodiments of the present disclosure are setforth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages of the present disclosure will beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plating bath filled with an electrolytic solutionfor electroforming a Ni—Cr alloy according to an embodiment of thepresent disclosure.

FIG. 2 illustrates an article comprising an electroformed Ni—Cr alloyaccording an embodiment of the present disclosure.

FIG. 3 is a flow chart of an electroforming Ni—Cr alloy process of thepresent disclosure.

The drawing(s) depict various preferred embodiments of the presentinvention for purposes of illustration only. One skilled in the art willreadily recognize from the following discussion that alternativeembodiments of the structures and methods illustrated herein may beemployed without departing from the principles of the inventiondescribed herein.

DETAILED DESCRIPTION

Electroforming is a metal forming process that forms self-supportingmetal parts or components through electrodeposition. Electroforming aNi—Cr alloy is a cost-effective and environmentally friendly method tomake some high temperature-resistant turbine engine components withcomplex geometries and tighter tolerance.

According to an aspect of the present disclosure, an electroformednickel-chromium (Ni—Cr) alloy for use as a turbine component isdisclosed. The Ni—Cr alloy comprises from 2 to 50 wt % chromium and thebalance nickel, and can be made thicker than at least 10 μm to formself-supporting turbine components. The Figure illustrates a platingbath containing an electrolyte solution for electroforming a Ni—Cr alloyaccording to an aspect of the present invention.

FIG. 1 illustrates a plating bath filled with an electrolytic solutionfor electroforming a Ni—Cr alloy according to an embodiment of thepresent disclosure Referring now to FIG. 1, there is provided a platingbath 102 containing an electrolytic solution that consists of a roomtemperature ionic liquid, namely deep eutectic solvent, includingcholine chloride, nickel chloride, chromium chloride, solvents, andsurfactants like anionic, cationic, or Zwitterionic (amphoteric)surfactants. The surfactant can be one of sodium dodecyl surfate,fluorosurfactants, cetyl trimethylammonium bromide (CTAB), or cetyltrimethylammonium chloride (CTAC). It is noted that the choline chloridebased metal processing is low-cost and environmentally friendly. In oneembodiment, a molar ratio of the choline chloride and chromium chlorideranges from 0.5 to 3.5. A turbine component is produced by depositing ametal onto a base form, known as a mandrel 104 which is removed afterelectroforming is done.

In the embodiment, polar aprotic and polar protic solvents are used toadjust the viscosity and conductivity of the plating bath 102 to attainhigh quality Ni—Cr alloy deposits. Specifically, protic solvents arepreferred due to their ability to donate hydrogen bonds. The solventsinclude formic acid, citric acid, Isopropanol (IPA), water, acetic acid,and ethylene glycol.

According to one embodiment, preferred solvent content is from 10 to 80vol % relative to the mixture of choline chloride and metal chloridesincluding the nickel and chromium chlorides on a pre-mixing basis.Referring to FIG. 1, electroforming the Ni—Cr alloy begins by providingan external supply of current to an anode and a cathode. The mandrel isthe cathode. The current can be a direct current (DC) or an alternatingcurrent (AC) including a pulse or pulse reverse current (not shown). Theregime and/or magnitude of the current can be controlled during thedeposition to achieve desired coating composition, density, andmorphology.

When the current is supplied, the metal at the soluble anode is oxidizedfrom the zero valence state to form cations with a positive charge.Metal cations, generally in complex forms in the presence of anions inthe solution, are reduced at the cathode to deposit in the metallic,zero valence state. The result is the effective reduction and transferof Ni and Cr ionic species from the electrolytic solution to the mandrel104. The mandrel 104 is removed after the electroforming is done.

The turbine component to be made is electroformed on the mandrel 104which is a cathode during electrodeposition. The anode is made of themetal to be plated on the mandrel, and includes a Ni—Cr alloy anode, aNi and/or Cr anode, or any combination of these materials can be chosento satisfy different requirements. An insoluble catalytic anode(catalyzing oxygen evolution, hexavalent chromium formation) ispreferable, but the anode used is not specifically limited. Acombination of soluble Ni anode and an insoluble catalytic anode can beused to control bath composition during the course of electrodepositionas well.

The mandrel is pre-treated prior to electrodeposition. The pre-treatmentincludes degreasing, cleaning the surface, and activation before beingplaced in the plating bath for electrodeposition. To enhance masstransport, the mandrel 104 can be moved in either a rotating orreciprocating mode or the electrolytic solution can be agitated duringthe electroforming process. The electroforming process inevitablydecomposes water in the bath 102, and thus the solution in the bath isreplenished to maintain consistent deposition quality.

FIG. 2 illustrates an article comprising an electroformed Ni—Cr alloyaccording an embodiment of the present disclosure. Feasibility of thickelectroformed Ni—Cr alloys has been demonstrated by electroforming aNi—Cr alloy which is thicker than 125 μm to make turbine components. Inone embodiment, an article 200 comprises an electroformed Ni—Cr alloy202 that includes from 2 to 50 wt % chromium balanced by nickel, and isthicker than at least 10 μm which was not attainable through theconventional methods.

In another embodiment, although not specifically limited, anelectroformed Ni—Cr alloy 202 comprises from 8 to 20 wt % chromiumbalanced by nickel. In the embodiment, the Ni—Cr alloy is thicker than125 μm to make a self-supporting turbine component. Optionally, aprotective coating 206 can be applied on a surface 204 of the Ni—Cralloy 202 to impart further oxidation resistance to the article 200. Theprotective coating 206 may include aluminum and a bond coat and otherthermal barrier coatings. Heat treatment may be performance on thestructure.

FIG. 3 is a flow chart of an electroformed Ni—Cr process of the presentdisclosure. Referring now to FIG. 3, forming a thick electroformed Ni—Cralloy to make turbine parts begins at step 300 where a part to be madeor a mandrel is pre-treated prior to electroforming a Ni—Cr alloy toremove foreign materials on the surface of the part of mandrel. At step302, a plating bath filled with a solution including a solvent, asurfactant, and an ionic liquid is provided. At step 304, the Ni—Cralloy is electroformed on the part or mandrel by providing an externalsupply of current to an anode and a cathode. The mandrel can be moved ina rotating or reciprocating mode during the electroforming process toincrease the deposition rate. The electroforming step 304 is done whenthe Ni—Cr alloy reaches the desired thickness.

After the electroforming is done at step 304, optionally, a protectivecoating 206 may be applied at step 306. In one embodiment, theprotective coating 206 may include a bond coat or a thermal barriercoating. The protective coating 206 may be applied to a surface 204 ofthe electroformed Ni—Cr alloy 202 at step 306 to impart oxidationresistance to the Ni—Cr alloy 202. The disclosed choline chloride basedelectroforming is a metal forming process that is cost-effective to makehigh temperature-resistant turbine parts with complex geometries andtighter tolerance, and is environmentally friendly.

It is to be understood that the disclosure of the present invention isnot limited to the illustrations described and shown herein, which aredeemed to be merely illustrative of the best modes of carrying out thedisclosure, and which are susceptible to modification of form, size,arrangement of parts, and details of operation. The disclosure isintended to encompass all such modifications which are within its spiritand scope of the invention as defined by the following claims.

1. An article comprising a turbine component electroformed of anickel-chromium (Ni—Cr) alloy including from 2 to 50 wt % chromiumbalanced by nickel, wherein the Ni—Cr alloy is thicker than 10 μm. 2.The article of claim 1, wherein the Ni—Cr alloy comprises from 8 to 20wt % chromium balanced by nickel.
 3. The article of claim 1, wherein theNi—Cr alloy is thicker than 125 μm.
 4. The article of claim 1, whereinthe turbine component is a rotor blade or a stator.
 5. The article ofclaim 1, wherein the turbine component is a vane. 6-20. (canceled)